Kinematic device for fire control against terrestrial targets with single rate sensor

ABSTRACT

In gun pointing a gun platform is driven by a tracker, but especially in military tanks, the gun platform is rarely horizontal. Accordingly, an elevational correction is necessary in addition to an azimuthal correction to lead a substantially horizontally moving target. The present device uses a single rate sensor to sense the azimuthal rate of the gun platform and a gravity sensor to detect the angle by which the gun platform is off of horizontal. The gravity sensor takes the form of a resolver which accepts the rate information to provide elevational and azimuthal gun pointing correction on such targets.

United States Patent inventor Appl. No. Filed Patented AssigneeKINEMATIC DEVICE FOR FIRE CONTROL AGAINST TERRESTRIAL TARGETS WITHSINGLE RATE SENSOR Primary Examiner-Samuel Feinberg AssistantExaminer-Thomas H. Webb Artomeys-James K. Haskell and Allen A. Dickey,Jr.

ABSTRACT: In gun pointing a gun platform is driven by a tracker, butespecially in military tanks, the gun platform is rarely horizontal.Accordingly, an elevational correction is necessary in addition to anazimuthal correction to lead a sub stantially horizontally movingtarget. The present device uses 5 Claims 1 Drawing a single rate sensorto sense the azimuthal rate of the gun plat- U.S. (1. 89/41 form and agravity sensor to detect the angle by which the gun Int. Cl. F41g 5/16,platform is off of horizontal. The gravity sensor takes the form F41 g1/00, F41 g 3/10 of a resolver which accepts the rate information toprovide Field of Search 89/41 .6, elevational and azimuthal gun pointingcorrection on such tar- 41.7 gets.

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26 7/44: 1 A: M17" l M16 0fl701 I KINEMATIC DEVICE FOR CONTROL AGAINSTTERRESTRIAL TARGETS WITH SINGLE RATE SENSOR BACKGROUND This invention isdirected to a kinematic lead angle mechanization for fire controlagainst terrestrial targets which employs a single rate sensor.

The problem or proper gun aiming against a substantially horizontallymoving terrestrial target, because of angularity of the gun platformwith respect to a plane normal to gravity has been recognized. Previousdevices employ a horizontal rate sensor for making azimuthal lead anglecorrections, and a separate elevational rate sensor to detect angularrate of the line of sight in a plane normal to the plane of the gunplatform for making elevation corrections. However, the departure of thegun platform from horizontal is usually slight so that the elevationalsignal is so small that noise signal from the elevational rate signaldetector is often more than the desired signal. Accordingly, elevationalcorrections have not been properly or correctly made.

SUMMARY In order to aid in the understanding of this invention, it canbe stated in essentially summary form that it is directed to a kinematiclead angle mechanization for fire control against terrestrial targetswhich employs a single rate sensor. The rate sensor measures theazimuthal rate of the gun platform, when the platform follows (tracks) ahorizontally moving target, and an angle detector determines the angulardisplacement of the gun platform from the horizontal. The rate and theangle are combined in a resolver to provide substantially correct valuesof target angular rate in the azimuthal and elevational directions.

Accordingly, it is an object of this invention to provide a kinematicmechanization for fire control against terrestrial targets which employsa single rate sensor. It is another object to provide a singlegyroscopic rate sensor on a gun platform. It is a further object toprovide means to sense the vertical direction, with respect to the gunplatform so that the angular deviation of the platform from a planeperpendicular to the vertical is established. It is a further object tocombine the rate sensor signal with the angular signal to evolve signalsfor directing the gun with respect to the line of sight so that properazimuthal and elevational corrections are made to correct for targetmotion. Other objects and advantages of this invention will becomeapparent from a study of the following portion of the specification, theclaims and the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic view showingan example of the angular relationship of the parts.

FIG. 2 is a schematic block diagram showing a mechanization forkinematic angle correction for fire control against terrestrial targetsemploying a single rate sensor.

DESCRIPTION I Referring to FIG. 1, the movable portion of a gun platformis illustrated at 10. It is, for example, a tank turret or is the gunmount portion that azimuthly in a field piece. A gun (not shown), whichis mounted upon the gun platform 10, is arranged such that it can rotateabout an axis in the plane of the platform 10, that is in theelevational direction. The azimuthal direction is illustrated at 12while the elevational direction is illustrated at 14. A line of sighttracker (not shown) drives the platform in the azimuthal direction, withrespect to its base, and drives the gun elevationally with respect tothe gun platform 10. Any convenient tracker can be employed, such asoptical, infrared, radar and the like. I I

Target 16 is a moving target and it is assumed that it is moving onlevel or substantially level ground. The direction of motion of target16 is illustrated at 18. The line 18 along which the target moves isperpendicular to the gravitational direction 20. The assumption that thetarget moves along a horizontal line is justified because largeterrestrial vehicles can move up and down grades only at slow rates, andhigh velocities are accomplished only on horizontal or substantiallyhorizontal terrain. Waterborne vehicles are confined to the watersurface.

From FIG. 1, it is seen that the plane of gun platform 10 is nothorizontal. When a gun is mounted upon an artillery piece, helicopter,ship or tank, the gun platform departs from the target plane defined bythe line of motion of the target 18 and the center of the gun platformby an angle 9. Thus, elevational correction as well as azimuthalcorrection must be made to lead a moving target. This invention providesthe necessary structure to provide sufficiently accurate lead signalsfrom a single rate sensing structure. Rate sensor 22 is mounted upon gunplatform 10 to measure the rate of rotation of the gun platform in theazimuthal direction. Making the assumption that the angular rate in theazimuthal plane is equal to the angular rate in the target plane, whichis nearly true for small values of the angle 6, then the angular rate ofthe target in both the azimuthal and elevational directions can becalculated, as is shown in the following equations 1 and 2:

where:

W angular rate of the target in the target plane W,, angular rate in theazimuthal direction W angular rate in the elevational direction Inproperly directing the gun, the total lead angle, the amount the gunmust lead the target when the target is moving, is equal to the angularrate times the time of flight of the projectile, as is given in thefollowing formulas 3 and 4:

where:

LE: W5 1 L lead angle in the azimuthal direction L lead angle in theelevational direction t= time of flight of the projectile Here it isassumed that the amount of lead in the azimuthal direction is equal tothe amount of lead in the target plane. Of course, this is anapproximation, but for small angles it is suffciently correct.

Referring to FIG. 2, a preferred mechanization of the present kinematiclead angle device for fire control against terrestrial targets with asingle rate sensor is illustrated. In FIG. 2, rate sensor 22 isillustrated as being a gyroscope, but it is clear that other ratesensors can be employed. Range is directly determined by range finder 24by an conventional means. From range, and ballistic information, thetime of flight t of the projectile is calculated in calculator 26. Thetime of flight is multiplied times the angular rate W, in multiplier 28so that the output of the multiplier is W, t.

Neglecting adder 30 for the moment, the W, 1 signal is fed into gravitysensor 32. Gravity sensor 32 is a resolver mounted on a platform 10 andhaving a pendulum 34 which is maintained in a direction parallel to thegravitational field. Pendulum 34 is connected to movable armature coils36 and 38. The effect of the gravitational sensing resolver 32 is tomultiply by the appropriate functions of the angle 6. Adder 30 is connected to armature coil 36, so that the outputs of the stator coils 40and 42 are in accordance with formulas 5 and 6 below:

L,(=W (cosO) t. (5)

L W (sin9) (6) In addition to the azimuthal and elevational leadnecessary to have the projectilestrike a moving target, ballistic andwind corrections must be made to gun pointing because of trajectoryconsiderations. Thus, in addition to the L and L values resulting fromresolver 32, other factors are also present in the output. Appropriateballistic values are placed a ballistic calculator 46, in accordancewith the characteristics of the round being fired, to develop aballistic correction B to account for the difference between theballistic trajectory nd and the line of sight. This is a verticalcorrection. Similarly, windage information is placed into windcalculator 44 to provide a windage or horizontal correction N clue towind. The output of wind calculator v44 goes to adder 30, while theoutput of ballistic calculator 46 goes to coil 38. Of course, both theballistic corrections and windage corrections must be corrected in termsof the gun platform angle 9. The total corrections are shown in thefollowing formulas 7 and 8:

D=Bsin9+(N+W t)cos9 (7) E=Bcos6(N+ W OsinG (8) where: D is the valuesubstantially corresponding to the angle in the platform plane betweenthe line of sight to the target and the direction of gun pointing for'astrike on the moving target as the platform is driven by platformrotator 48.

E is the value substantially corresponding to the angle in a planenormal to the platform plane between the line of sight to the target andthe direction of gun pointing for strike on the moving target.

This invention having been described in its preferred embodiment, it isclear that it is susceptible to numerous modifications and embodimentswithin the ability of those skilled in the art and without the exerciseof the inventive faculty. Accordingly, the scope of this invention isdefined by the scope of the following claims.

1. A kinematic device utilizing the local gravity vector and thehorizontal plane normal to the local gravity vector for thedetermination of the angular rate of rotation in azimuthal andelevational directions to a target of a platform rotatable about an axisand having a platform plane therethrough normal to the axis of rotation,said device comprising:

a single angular rate sensor mounted on said platform for providing asignal proportional to the angular rate of rotation of said platformaround its axis;

vertical sensor means mounted on said platform for providing a signalindicating angular orientation of said platform with respect to thehorizontal plane;

resolver means connected to said rate sensor; and

said resolver means including a movable portion coupled to said verticalsensor means, said resolver means resolving signals from said ratesensor and said vertical sensor means so that said resolver means emitsa first signal corresponding to the angular rate of rotation of saidplatform in the azimuthal direction and a second signal corresponding tothe angular rate of said platform in a plane normal to the plane of saidplatform as said platform is rotated.

2. The device of claim 1 wherein said platform is a gun platform, with agun rotatable in an azimuthal direction with said platform in saidplatform plane and being rotatable in an elevational direction in anelevational plane normal to said plane of said platform, said resolvermeans emitting a signal proportional to the angular rate of said gunplatform in the azimuthal direction times a function of the anglebetween said platform plane and said horizontal plane for azimuthalcorrection of gun pointing and emitting a signal corresponding to theangular rate of aid gun platform times another function of said anglebetween said platform plane and said horizontal plane for elevationalcorrection of gun pointing.

3. A kinematic device for fire control against terrestrial targets, saiddevice comprising:

a gun platform having a platform plane and means to rotate said platformabout an axis normal to said platform plane, said gun platform beingadapted to carry a gun elevatable in adirection normal to said platformplane;

a single rate sensor mounted on said platform, said rate sensor sensingangular rotation of said platform about its axis and emitting a signalproportional to the rate of rotation of said platform about its axis;

angular detecting means mounted on said platform for detecting theangular difference between the axis of rotation of said platform and thegravitational direction; and said rate sensor being coupled to saidangular detecting means so that said angular detecting means emits asignal proportional to the angular rate of said platform about its axistimes a function of the angle between said platform axis and thegravitational direction ,and a signal proportional to the angular rateof said platform about its axis times another function of the anglebetween said platform axis and the gravitational direction, the signalsemitted form said angular detecting means being employed for gunpointing correction.

4. The device of claim 3 further including first means for calculatingtime of flight of a projectile from said gun to a selected target andsecond means coupled to said first means, rate sensor and angulardetecting means for multiplying the time of flight of the projectiletimes the angular rate of rotation of said gun platform to develop aproduct signal, wherein said angular detecting means is a resolver, saidresolver being responsive to the product signal from said second meansfor emitting a signal substantially corresponding to azimuthal leadcorrection and a signal substantially corresponding to elevational leadcorrection.

5. A single sensor kinematic device forfire control againstsubstantially horizontally moving targets, said device comprisaplatform, said platform being rotatable on an axis and having anazimuthal plane normal to the platform axis, drive means to rotate saidplatform in its plane on its axis, drive means to rotate said platformin its plane on its axis, said platform being a gun platform, a gunmounted on said platform for rotation with said platform in theazimuthal plane, said gun being mounted on said platform for rotation inan elevational plane normal to said azimuthal plane; angular ratesensing means mounted on said platform, said angular rate sensing meanssensing and emitting a signal proportional to the angular rate of.rotation of said platform about its axis;

verticality sensing means mounted on said platform for sensing the anglebetween said azimuthal plane and a horizontal'plane; range sensing meansfor determining the range between said platform and a target; time offlight calculating means connected to said range sensing means foremitting a signal proportional to the time of flight of a projectilefrom said gun to the target; multiplying means coupled to said angularrate sensing means and to said time of flight calculating means formultiplying the time of flight signal times the angular rate signal toproduce a product signal; and

resolver means coupled to said multiplying means and said verticallysensing means and being responsive to the product signal for producing asignal proportional to azimuthal gun lead angle and a signalproportional to elevational gun lead angle.

53 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 6Dated March 2, 1971 Inventor(s) Millard M. Frohock, Jr.

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Col. 1, line 64, after that and before "azimuthly" insert -swings. Col.2 line 25, W W (cos 6) 5 W (cos 6 should be W W (cos 6) W (cos 6) (1)-Col. 2 line 26, W W (-sin6) 2 W (-sin K should be W W sin 6) W sin 6)Col. 2 line 35, delete "where".

Col. 2 lines 36 through 38, "L W t(3) L w U4) E i L Eead angle in theazin direction" should be A w t (3) L =W t (4) E w ere. L lead angle inthe azimui direction-- 2 Col. 2 line 50, "an" should be -any.

Col. 2 line 67, "L 2 W (-sin 6) (6) should be L "5 W (-sin 6) t (6)--Col. 2, line 73, after "placed" and before "a insert -in- C01. 3, line1, "nd" should be -and--.

Col. 3, line 60, "aid" should be -said-.

Col. 4, line 19, "form" should be --from-.

Col. 4, line 37, delete "drive" I Col. 4, line 38, delete "means torotate said platform in plane on its axis,".

Col. 4, line 61, "vertically" should 'be verticality- Signed and sealedthis 10th day of August 1 971 (SEAL) Attest:

EDWARD I-I.FLETGHER,JR. WILLIAM E. SCHUYLER, JR.

Attesting Officer Commissioner of Patents

1. A kinematic device utilizing the local gravity vector and thehorizontal plane normal to the local gravity vector for thedetermination of the angular rate of rotation in azimuthal andelevational directions to a target of a platform rotatable about an axisand having a platform plane therethrough normal to the axis of rotation,said device comprising: a single angular rate sensor mounted on saidplatform for providing a signal proportional to the angular rate ofrotation of said platform around its axis; vertical sensor means mountedon said platform for providing a signal indicating angular orientationof said platform with respect to the horizontal plane; resolver meansconnected to said rate sensor; and said resolver means including amovable portion coupled to said vertical sensor means, said resolvermeans resolving signals from said rate sensor and said vertical sensormeans so that said resolver means emits a first signal corresponding tothe angular rate of rotation of said platform in the azimuthal directionand a second signal corresponding to the Angular rate of said platformin a plane normal to the plane of said platform as said platform isrotated.
 2. The device of claim 1 wherein said platform is a gunplatform, with a gun rotatable in an azimuthal direction with saidplatform in said platform plane and being rotatable in an elevationaldirection in an elevational plane normal to said plane of said platform,said resolver means emitting a signal proportional to the angular rateof said gun platform in the azimuthal direction times a function of theangle between said platform plane and said horizontal plane forazimuthal correction of gun pointing and emitting a signal correspondingto the angular rate of aid gun platform times another function of saidangle between said platform plane and said horizontal plane forelevational correction of gun pointing.
 3. A kinematic device for firecontrol against terrestrial targets, said device comprising: a gunplatform having a platform plane and means to rotate said platform aboutan axis normal to said platform plane, said gun platform being adaptedto carry a gun elevatable in a direction normal to said platform plane;a single rate sensor mounted on said platform, said rate sensor sensingangular rotation of said platform about its axis and emitting a signalproportional to the rate of rotation of said platform about its axis;angular detecting means mounted on said platform for detecting theangular difference between the axis of rotation of said platform and thegravitational direction; and said rate sensor being coupled to saidangular detecting means so that said angular detecting means emits asignal proportional to the angular rate of said platform about its axistimes a function of the angle between said platform axis and thegravitational direction and a signal proportional to the angular rate ofsaid platform about its axis times another function of the angle betweensaid platform axis and the gravitational direction, the signals emittedform said angular detecting means being employed for gun pointingcorrection.
 4. The device of claim 3 further including first means forcalculating time of flight of a projectile from said gun to a selectedtarget and second means coupled to said first means, rate sensor andangular detecting means for multiplying the time of flight of theprojectile times the angular rate of rotation of said gun platform todevelop a product signal, wherein said angular detecting means is aresolver, said resolver being responsive to the product signal from saidsecond means for emitting a signal substantially corresponding toazimuthal lead correction and a signal substantially corresponding toelevational lead correction.
 5. A single sensor kinematic device forfire control against substantially horizontally moving targets, saiddevice comprising: a platform, said platform being rotatable on an axisand having an azimuthal plane normal to the platform axis, drive meansto rotate said platform in its plane on its axis, drive means to rotatesaid platform in its plane on its axis, said platform being a gunplatform, a gun mounted on said platform for rotation with said platformin the azimuthal plane, said gun being mounted on said platform forrotation in an elevational plane normal to said azimuthal plane; angularrate sensing means mounted on said platform, said angular rate sensingmeans sensing and emitting a signal proportional to the angular rate ofrotation of said platform about its axis; verticality sensing meansmounted on said platform for sensing the angle between said azimuthalplane and a horizontal plane; range sensing means for determining therange between said platform and a target; time of flight calculatingmeans connected to said range sensing means for emitting a signalproportional to the time of flight of a projectile from said gun to thetarget; multiplying means coupled to said angular rate sensing means andto said time of flight calculating meanS for multiplying the time offlight signal times the angular rate signal to produce a product signal;and resolver means coupled to said multiplying means and said verticallysensing means and being responsive to the product signal for producing asignal proportional to azimuthal gun lead angle and a signalproportional to elevational gun lead angle.